1. Field of the Invention
The present invention relates to a motor.
2. Description of the Related Art
A disk drive apparatus, such as, for example, a hard disk drive, is typically equipped with a motor (i.e., an FDB motor) including a fluid dynamic bearing. In the FDB motor, a lubricating oil is arranged between a sleeve of a stationary portion and a shaft of a rotating portion. A dynamic pressure groove is defined in an inner circumferential surface of the sleeve or an outer circumferential surface of the shaft, and while the motor is running, the dynamic pressure groove induces a dynamic pressure in the lubricating oil. This allows the rotating portion including the shaft to rotate with high precision.
Thus, in recent years, FDB motors have sometimes been used also in applications other than disk drive apparatuses. However, when the FDB motor is used in an application other than the disk drive apparatus, an additional component, such as, for example, a flywheel, is sometimes attached to the rotating portion of the FDB motor. Such an additional component changes the axial height of the rotating portion. If the axial height of the rotating portion becomes high, the runout of the rotating portion becomes significant while the motor is running, which makes it difficult to stabilize the posture of the rotating portion.